Some pool safety devices employ sensors of pool surface disturbance caused by a person falling into the pool. One device employs a diaphragm to detect the resulting displacement wave. Another device senses the underwater sound generated by the object falling into the pool. Another device is attached to a potential drowning victim and alerts when the device gets wet. Another device uses the break in a laser beam caused by an object moving across the beam when approaching the pool.
These devices are limited by a number of disadvantages. For example, if the device is mounted on the side of the pool, it restricts free motion about the pool. If the device is mounted under the surface of the water, it restricts access to solar energy and attenuating direct RF communication. If the device must be worn by a cooperating person, it excludes application to most uncooperative potential drowning victims such as unattended children. Most prior art devices require periodic maintenance for alignment, and battery change. As some prior art devices require wires for connectivity to control boxes and alarms, they present a poolside hazard or requiring modifications to the pool construction. Alarm information has not been remotely available. Prior art devices have had no means to adapt their detection criteria and reduce false alarms, nor of improving detection speed and sensitivity.